This invention relates to a disk array system using RAID, and more particularly to a disk array system which is capable of identifying user data of a disk device.
A general disk array system includes a plurality of disk devices, which form a RAID structure. For example, in RAID 5, a given piece of data is divided to be written to a plurality of disk devices simultaneously. In other words, data is previously divided into pieces each having a predetermined size (stripe size), and the divided pieces of data are written to sectors of disk devices. Written to one of the plurality of disk devices is a parity (redundant data) of the data that has been written to another disk device.
Accordingly, in the disk array system, redundant data is created and stored in the disk device so as to allow data to be restored even when a failure occurs in the disk device. Another system is known, in which a guarantee code is appended to each logical data block in order to enhance the reliability of the entire disk array. Specific examples include, as noted in JP 2001-202295 A and JP 2000-347815 A, a method in which, when data is written to a disk device, the guarantee code composed of a logical address value LA (Logical Address) and an exclusive-OR LRC (Longitudinal Redundancy Check) is appended to the data on a logical data block basis, and the resultant data is written to the disk device, and when the data is read out from the disk device, the LA value and LRC value that are appended to each logical data block are checked, thereby checking whether or not an address error or a data error has occurred within the disk device.